The present invention relates to an automotive seat back. More particularly, it relates to an automotive seat-back structure which is capable of protecting a passenger""s neck vertebra when the passenger""s vehicle is run into from behind and which allows the passenger""s lumbar vertebra to be pressed usually.
As the conventional automotive seat back of this kind, International Patent Publication No. WO 98/09838 discloses one seat back structure which comprises a rectangular seat-back frame, supporting means on the top of the seat-back frame, which is capable of swiveling back and forth and also shifting up and down, a headrest adapted so as to move back, forth, up and down and also carried by the upper end of the supporting means through a headrest holder attached to a stay, and an actuating member carried by the lower end of the supporting means and also capable of moving only by an impact pressure by the passenger""s back.
Therefore, for example, when the passenger""s vehicle has a collision from behind, then the seat back is subjected to an impact load directing forward and also a reactionary load due to the passenger""s back, directing backward. In detail, the above loads are applied on a back element constructed in the seat-back frame and the actuating member as well. Then, the backward movement of the actuating member causes the upper end of the supporting means to be rotated in front about an upper side of the seat-back frame as a pivotal fulcrum and also to be shifted upward, so that the headrest on the upper end of the supporting means moves in a direction approaching the passenger""s head.
Accordingly, even if the vehicle collision from behind causes the seat back to be bent backward due to the reactionary load of the passenger, the headrest instantaneously approaches the passenger""s head to accept it certainly, whereby the passenger""s neck can be protected.
In this way, the above-mentioned prior art structure is effective against the unusual vehicle""s rear-end collision. However, if a lumbar supporting member for usually supporting the passenger""s lumbar is also arranged in such a limited space of the seat-back frame, then the arrangement causes either or both of the lumbar supporting member and the actuating member to be small-sized, accompanying the unsatisfied constitution of the seat back structure. Consequently, an improvement in commercialization would be necessary in the seat back structure.
Under the above circumstance, it is an object of the present invention to provide an automotive seat-back structure which aims at the protection of the passenger""s neck vertebra at the vehicle""s rear-end collision and also the usual supporting of the passenger""s lumbar vertebra, with satisfaction.
According to the invention, the above-mentioned object is accomplished by an automotive seat-back structure comprising a seat-back frame, supporting means carried by the seat-back frame, the supporting means being capable of swinging back and forth against an upper end of the seat-back frame and also capable of moving up and down against the upper end of the seat-back frame, a headrest supported by an upper end of the supporting means, an actuating member carried by a lower end of the supporting means, the actuating member being movable on only receipt of an impact pressure by a passenger""s back, a first supporting member carried by a lower end of the seat-back frame, a second supporting member carried by either one of the actuating member and the supporting means, and a lumbar supporting member carried by the first supporting member and the second supporting member to support the passenger""s lumbar vertebra on pressure, the lumbar supporting member being rotatable back and forth and also movable up and down.
With the arrangement mentioned above, when the actuating member is subjected to a load by the rear-end collision of the passenger""s vehicle, then the supporting means allows the headrest to be moved forward and upward, thereby holding the passenger""s neck vertebra.
Additionally, since the lumbar supporting member is carried by the actuating member and the supporting means through the second supporting member, the lumbar supporting member on receipt of no impact pressure is capable of supporting the passenger""s lumbar vertebra as well as the member""s movement due to the only receipt of impact pressure through the passenger""s back.
According to the second feature of the invention,the lumbar supporting member comprises a lowermost part which is engageable with the first supporting member, an uppermost part which is engageable with the second supporting member, and first urging means formed in one body with a main part of the lumbar supporting member, the main part being capable of projecting forward to support the passenger""s lumbar vertebra on pressure, the first urging means being adapted so as to encourage the main part""s returning from its projected position.
According to the third feature of the invention, the automotive seat-back structure further comprises a yoke bar carried by the lowermost part of the lumbar supporting member, the yoke bar being capable of swinging against lowermost part of the lumbar supporting member, second urging means connected to one end of the yoke bar, for always urging the one end of the yoke bar upward, and operating means operatively connected to another end of the yoke bar, wherein the operation of the operating means allows the main part of the lumbar supporting member to be moved in opposition to the first urging means and the second urging means.
Accordingly, if only manipulating the operating means so as to project the main part, the passenger""s lumbar vertebra can be supported by the so-moved lumbar supporting member in opposition to the first and second urging means.
According to the fourth feature of the invention, the first supporting member and the second supporting member are together made from wires.
Owing to the characteristics of wires, when the lumbar supporting member projects into deformation and also returns to the substantially-flattened position, it is possible to ensure the smooth rotations of the first and second supporting members.
According to the fifth feature of the invention, the supporting means comprises a pair of armature pipes arranged inside the seat-back frame so as to extend up and down.
According to the sixth feature of the invention, the main part of the lumbar supporting member includes a pair of first members separated from each other so as to extend up and down and a plurality of second members extending over the first members and the first urging means includes a pair of plate springs arranged along the first members respectively, thereby to urging the main part.
According to the seventh feature of the invention, the second urging means is in the form of a coil spring.
According to the eighth feature of the invention, the operating means comprises a cable connected to the other end of the yoke bar, a retractor allowing the cable to be wound thereinto, and a manipulating lever for operating the retractor to wind and rewind the cable.
These features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompany drawing.